Innumerable laminated decorative films, such expression as used herein including the reflective and retroreflective laminated films, are known to the prior art and such have been widely used for innumerable industrial and commercial purposes including decals, signs, posters, highway signs, traffic markers, artists' layout materials, etc. Such laminates typically include a layer of decorative particles (e.g. metal flake, pigment, glass beads, etc.) adhered to or between a layer or layers of plastic film or between a layer of plastic film and a support layer such as a layer of suitable release paper.
The laminated films are also made by virtually innumerable specific methods, but such methods typically have the common feature of using what is commonly referred to as an adhesive solution or an adhesive in solution, i.e. an adhesive including a solvent such as water, MEK (methyl-ethyl-ketone), toluol, acetone, alcohol, naptha, etc., such adhesive sometimes referred to in the art as a wet adhesive. In typical prior art practice, either a layer of wet adhesive is applied to a support surface, such as a layer of plastic film or release paper, and a layer of decorative particles is applied over the wet adhesive, or the decorative particles are immersed or suspended in a wet adhesive and the mixture of wet adhesive and decorative particles is applied to a support layer, such decorative particles sometimes said to be in solution. Prior art laminates and methods of making the same, of the type noted above, are discovered in U.S. Pat. Nos. 2,748,019; 3,399,070; 3,536,551; 3,560,294; 3,749,629; 3,873,390; 4,032,291; and 4,104,102.
Refererring more particularly to the prior art, and specifically to the prior art method of making laminated film illustrated diagrammatically in FIG. 1, decorative particles in solution indicated generally by numerical designation 10 are applied in a layer to the bottom surface of a layer of clear plastic film 12 by a transfer roll 16 as the film advances from a let-off roll 14 between the transfer roll 16 and a pressure roll 18. Thereafter, the plastic film now having the layer 10 of decorative particles in solution on its top surface after passing over the pressure roll 18 is advanced between a pair of nip rollers 20-22 where it is laminated to a layer of release paper 24 advancing from a letoff roll 26 whereupon the lamination is advanced and taken upon a suitable take-up roll 28. Various problems are known to the prior art method illustrated in FIG. 1, e.g. there must be chemical compatibility between the decorative particles and the wet adhesive, particularly between the decorative particles and the solvent, or else the solvent will degrade the particles sometimes to the point of ruination such as by dissolving, or partially dissolving, the particles. Further, when such decorative particles are immersed or suspended in the wet adhesive there is a settling problem due to the fact that the decorative particles and the wet adhesive have different specific gravities or densities and hence the particles tend to settle out preventing the application of a uniform mixture of decorative particles and wet adhesive; a similar problem is that of viscosity which can be caused by varying concentrations of the decorative particles and wet adhesive. Still further, since the adhesive is a wet adhesive as described above, temperature problems can arise requiring the process to be performed in a controlled temperature environment which, of course, can add unwanted expense to the cost of manufacture and hence to the cost of the end product.
A further method known to the prior art for producing such decorative foils or lamainates includes the step of applying a liquid film of plastic material over the decorative particles whereby upon solidification of the liquid film to form a solid a sheet-locked matrix of particles and plastic is provided; this process is known to have the problem of non-uniform scattering of the particles throughout the thickness of the film whereby unwanted variations in color or visual appearance are presented.
As is further known to those skilled in the art, various industrial and commercial uses of such decorative films or laminates require, or make it highly desirable for various reasons such as cost, that the decorative film or laminate be thermal die cuttable instead of requiring cutting by the more expensive steel rule die process.
Accordingly, there exists a need in the laminated decorative film art for a laminated decorative film wherein the decorative particles are provided in a more uniform layer and for a method for making the same wherein the above-noted problems of chemical compatibility, settling, viscosity, and temperature environment, etc. are overcome. Still further, there exists a need in the art for a decorative laminated film which is thermal die cuttable.